This invention relates to airbag arrangements for motor vehicles having controlled deployment of the airbag to protect an occupant.
Airbag arrangements for motor vehicles having one or more airbags are known in a wide variety of embodiments and for a wide variety of purposes. One component of these conventional arrangements may be a sensor system that determines the sitting position of the occupant to be protected in relation to the airbag in order to control the deployment of the airbag and the timing and extent of air bag deployment based on that determination. German Offenlegungsschrift No. 44 20 114 discloses an air bag arrangement for front and side protection having control electronics arranged for determining the direction and intensity of an impact as well as the seat occupancy and controlling the actuation of airbags individually or in combination based on the result of the determination.
Some conventional airbags are arranged behind a cover in an instrument panel that is opened to release the airbag and, in addition to providing protection for the upper body of a seat occupancy, providing protection for the occupant's knees as well. In the arrangement disclosed in U.S. Pat. No. 4,948,168, upon deployment of an airbag, a knee pad located behind the instrument panel trim is swung out of a rest position into a position adjacent to the occupant's knees. The knee pad may alternatively have the configuration of a flap, covering a storage compartment for the folded airbag and forming a part of the lower instrument panel trim which is joined to the overlying portion of the instrument panel trim by a tear edge or weak spot. In addition to the airbag for protection of the upper body, an auxiliary air bag for knee protection may be connected to the gas generator so as to project between a supporting wall integral with the vehicle frame and the protecting position of the knee pad in the activated condition.
Additionally, U.S. Pat. No. 4,394,033, discloses an airbag arrangement having a pressure-relieving device to render the airbag deployment as independent of temperature fluctuations as possible. This patent also shows that an airbag can be arranged so that it is able to protect both the upper body and the knees of the occupant.
Pressure relief valves are also employed to control the flow rate of gas to the airbag as a function of the seated position of the passenger, for example to diminish the gas flow if the occupant at the time of impact is not in his predetermined seated position but is leaning forward, i.e. is "out of position" so that the airbag will not act on the occupant with full gas pressure. To control the gas pressure in an airbag, step generators may also be employed, though they are rather costly.
Lastly, Canadian Patent No. 1,080,764 discloses an airbag arrangement disposed underneath the instrument panel which includes a hollow member providing knee impact protection and an airbag for protection of the occupant's upper body.